European Council President Donald Tusk accused him of criticising Europe “almost daily”, tweeting: “Dear America, appreciate your allies, after all you don’t have that many.”

What exactly did Trump say about Germany?

Germany has the EU’s biggest economy and has long been accused by US administrations of failing to contribute its fair share to Nato operations but Mr Trump’s comments were particularly stinging.

At a breakfast meeting in Brussels with Nato chief Jens Stoltenberg, the US leader said: “Germany is totally controlled by Russia because they will be getting from 60% to 70% of their energy from Russia, and a new pipeline, and you tell me if that’s appropriate because I think it’s not and I think it’s a very bad thing for Nato.”

Germany has given political support for a new Baltic Sea pipeline, Nord Stream 2, which will increase the flow of Russian gas to EU states. The project has been sharply criticised by Poland and others.

The US president also accused Germany of only spending “a little bit over 1%” of its economic output on defence compared to the 4.2% spent by the US “in actual numbers”.

How did Merkel respond?

“I want to say that I have experience of when a part of Germany was controlled by the Soviet Union,” she told reporters.

“I am very happy that today we are united in freedom as the Federal Republic of Germany. Because of that we can say that we can make our independent policies and make independent decisions. That is very good, especially for people in eastern Germany.”

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Mrs Merkel (centre) led efforts to negotiate with Mr Trump over trade at last month’s G7 summit in Canada

Mr Stoltenberg sought to play down Mr Trump’s accusations, saying he expected Nato leaders would agree they were “stronger together than apart”.

Moscow’s potential influence

By Jonathan Marcus, BBC defence and diplomatic correspondent

In describing Germany as being “totally controlled by Russia” and linking this to what the US sees as Berlin’s unsatisfactory defence budget, President Trump is underscoring two long-standing US concerns.

US leaders have long warned of what they see as Europe’s uncomfortable dependence upon Russian energy supplies. And they have also been arguing for more than a decade that the Europeans should spend more on defence. Mr Trump has given these twin themes a new and more abrasive tone.

While he may well be overstating Germany’s dependence upon Russian energy, even many European leaders are well aware of the potential influence that this could give Moscow. It’s an area where short-term economic and longer-term security considerations are at variance.

No wonder then that when the US sanctions Russia for its behaviour in Ukraine and its annexation of Crimea it included steps to hamper anyone who helped build or support new Russian pipelines westwards.

What is the spending row about?

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German troops in Lithuania this summer

Mr Trump’s main objection is that all but a handful of member states have still not increased their defence budgets to meet a goal of spending at least 2% of their annual economic output on defence by 2024.

Many countries in NATO, which we are expected to defend, are not only short of their current commitment of 2% (which is low), but are also delinquent for many years in payments that have not been made. Will they reimburse the U.S.?